Switch operating mechanism



y 1954 s. LINDELL SWITCH OPERATING MECHANISM 3 Sheets-Sheet 1 Filed Nov. 14, 1950 INV ENTOR.

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" SWITCH OPERATING MECHANISM Filed Nov. 14, 1950 s Sheets-Sheet 2 BUM/ 5f? IN VEN TOR.

.igam zzmai z Y v July 27, 1954 s, UNDELL 2,685,004

SWITCH OPERATING MECHANISM Filed Nov. 14, 1950 3 Sheets-Sheet 3 I ROTATABL E STATIIONARY INSULATOR INSULATOR FIG. 5

SWITCH FULLY OPEN MOVEMENT OF SWITCH BLADE 26 AWAY FROM CLOSED POSITION MAIN CONTACTS ENGAGED OR DISENGAGED 97 INTERRUPTER 99 UNITS OPERATED MOVEMENT OF TOGGLE LINK 83 FEGO ATTORNEY INVENTOR SIGURD l. LINDELL Patented July 27, 1954 UNITED STAT ?ATENT OFFICE Sigurd I. Lindell, Chicago, 111., assignor to S. & 0. Electric Company, Chicago, Ill., a corporation of Delaware Application November 14, 1950, Serial No. 195,510

9 Claims. 1

Thi invention relates, generally, to mech anisms for operating high voltage electric power switches and it has particular relation to mesh anisms for operating switches of the general character disclosed in the copending application of Lindell, Serial No. 41,597, filed June 38, 1948, and of Kojis, Serial No. 158,246, filed April 26, 1950, now Patent No. 2,613,291, issued October '7, 1952, both assigned to the assignee of this application.

These switches usually are assembled in units of three for gang operation on a three phase cir-- cuit. Each switch unit includes a base on are mounted three insulators. The central insulator i rotatable and carries a switch blade for engagement at either end with main sw' ch contacts that are supported on the outlying insulators on the base. In order to avoid arcing on opening or closing of the main contacts, each of the outlying insulators also carries a load interrupter to which the current flowing through the main contacts is transferred prior to opening thereof. The load interrupter is designed to quickly and efficiently interrupt the are which is formed on separation of its contacts and for quickly closing the circuit when its contacts are closed.

Preferably the main contacts are designed and constructed so that they engage under relatively high pressure. The purpose of this is to minimize losses incident to current flow through the main switch contacts. In order to disengage or engage the main switch contacts a relatively great force must be applied to the switch blade, However, this force need be applied only during a relatively small portion of the full movement of the switch blade from or to switch closed position.

The load interrupter on each of the outlying insulators is operated by the switch blade in its movement from or to the switch closed position. It is desirable that its contacts be separated at a relatively high speed for the purpose of effecting a corresponding rapid extinction of the are drawn therebetween.

From the foregoing it will be a parent that the movement of the switchblade from and to the switch closed position where the main contacts are disengaged and engaged, a relatively great force must be applied during a relatively small .portion of the total travel of the switch .Also it will be apparent that the movement of the switch blade must be accelerated rapidly in order to effect the desired high speed operation "of the load interrupter for-opening orblos'ing the circuit therethrou'g-h.

Accordingly, among the objects of this invention are: To provide for operating each switch .unit and for operating them in unison in a simple, efficient and economical manner; to interconnect driving means and the blade of each switch unit in such manner as to operate "the switch blade with sufficient force to disengage and engage the .main' switch contacts during a relatively small movement of the switch blade and to accelerate the movement of the switch blade relative to the driving means while the former is operating the load interrupter; to employ a toggle linkage for accomplishing these functions; to arrange the toggle linkage so that the links thereof are in about .end-to-end centered relation when the associatedswitch is closed; to limit the movement of the toggle linkage slightly past the center position so as .to lock the switch blade individual thereto in the switch closed position; to pivot one of the links of the toggle linkage on the base carrying the insulators on which the switch blade and switch contact are mounted; to apply a turning moment to this one link for operating the corresponding switch blade from and to the switch closed position; and to apply the force for moving the toggle linkage to operate the switch blade individual theretolat the pivoted connection between the toggle links at substantially right angles to the center line of the switch base .individual thereto.

Other objects of this invention will, in part,'b'e obvious and in part appear hereinafter.

This invention is disclosed in the embodiment thereof shown in the accompanying drawings and it comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the constructionhereinafter set forth and the scope of the application of which Will be indicated in the appended claims.

For a more complete understanding of the nature and scope of this invention, reference can be had to the following detailed description, taken together with the accompanying drawings, in which:

Figure 1 is a view, in front elevaton, of a typical installation of an operating mechanism for each of three switch units mounted on a-suitable support for gang operation;

Figure 2 is ;a view, in side elevation, of the assembly illustrated in Figure 1 Figure 3 is a view, .in side elevation, of one the switch units, the switch being shown in the closed position;

Figure 4 is a detail sectional View taken gen erally along the line 4-4 ofF'igure 3 and illustrating how the operating mechanism is intercomnected between the base and the rotatable insulator for operating the latter to swing the switch blade in the manner outlined hereinbeiore and described in detail hereinafter;

Figure 5 is a View which illustrates diagrammatically the manner in which the toggle linkage performs its function in rotating the switch blade out of and into switch closed position; and

Figure 6 shows curves which demonstrate relationship between the movement of one of toggle links of the operating mechanism and movement of the switch blade.

Referring now particularly to Figure l of the drawings, it will be observed that the reference character it designates, generally, a frame carrying cross beams H on which switch units, shown generally at i2, are mounted. It will be noted that three switch units 12 are illustrated, this being the arrangement which is used customarx for switching three phase alternating currc circuits. The present invention is illustrated in conjunction with apparatus intended for use on circuits operating at voltages of the order of 23,000 volts and above. However, this is men tioned by way of illustration rather than limitation.

Each switch unit l2 includes a channel iron base it at the ends of which stationary insulators Hl are mounted. Intermediate the stationary insulators I4 is a rotatable insulator !5 the movement of which controls the operation of the switch unit l2. A toggle operating mechanisi shown generally at it, is employed for rotating the insulator E5 to accomplish this function. The details of construction and manner of operation of the toggle operating mechanism ill will be set forth hereinafter.

Since three switch units [2 are employed and it is desirable to operate them in unison, the toggle operating mechanisms is are interconnected by interphase rods ll. A rod i8 interconnect the toggle operating mechanism of the left hand switch unit 12, as shown in Figure l. and one arm of a bell crank is that is mounted on a suitable channel 2c which is carried by the cross beams I l. The other arm of the bell crank I9 is connected by a rod 2! to an o crating handle 22 which is located in a position where it can be manually operated by a lineman. While the present invention is illustrated as being arranged for manual operation it will be understood that, if desired, suitable power driven mechanism can be employed in lieu of the man ually operated handle 22.

As illustrated more clearly in Figure 3 the rotatable insulator i5 carries at its upper end switch blade 26. Preferably the switch blade is in the form of a tube of good conducting material such a copper and it i secured by a clamp 21 to the upper end of the rotatable insulator 55. At each end of the switch blade 25 there is provided a blade tip as set forth in detail in said Lindell application. The blade tip includes a main contact arm which is arranged to make contact engagement with a stationary main contact member that is illustrated, generally, at It will be noted that the stationary main contact member 3&3 is mounted on a terminal bracket 2% which is secured to the upper end of each of the stationary insulators [4. Each terminal bracket 3! includes a terminal pad 32 formed integrally therewith to permit connection to the circuit associated therewith.

In order to avoid any arcing between the main contact arm and the contact fingers cooperating the the the therewith when the circuit therethrough is opened or closed, a load interrupter, shown generally at 42 is employed. The load interrupter 12 is carried y an angle bracket, mounted on the terminal bracket 34.

From the foregoing escription it now will be apparent that the switch blade 28 in it movement from and to the switch closed position must perform mechanically certain functions which are widely different. When the main contact arm is moved out of or into contact engagement with the contact fingers, a relatively great force must be exerted. As previously indicated, this force must be increased under certain conditions. It i also desirable that the load interrupter be operated at a high speed. This is particularly desirable when the switch blade is moved toward the switch open position and an arc is drawn and must be extinguished within the load interrupter 62. Accordingly, the movement of the switch blade must be accelerated greatly during the portion of its movement where the contacts of the load interrupter are opened at high speee. After the current flow has been interrupted by the load interrupter 42, provision must be made for swinging the switch blade 2?) to a position substantially at right angles to its switch closed The purpose of this is to provide maximum disconnect distance between the energized t rminals of each of the switch units !2 when the switch is in the open position. However, this final movement of the switch blade 26 to the full open position can be at less mechanical advantage than is required for the operation thereof in disengaging or engaging the main contacts comprising the main contact arm 2% and the stationary main contact member 38 and for operating the load interrupter d2. 7

The toggle operating mechan sm it associated with each of the rotatable insulators iii permits the operation of each of the switch blades 23 in the manner described to accomplish these ends. This mechanism is illustrated in more detail in Figure 4 of the drawings. As there shown each of the rotatable insulators i5 is provided at its base with an arm is. In Figure 4 the arm if? is shown in the position which it occupies when the associated switch. blade 26 is in the s ch closed position. The toggle operating mecha in if: is arranged to swing the arm is and there. the insulator l5 and switch blade a clockwise direction through an arc of ninety s. For this purpose the arm it is pivotally connected at 86 near its outer end to a relatively short link 3 I which, in turn, is pivotaliy connected at 8'2 to a relatively long toggle link 83. The latter toggle link is mounted to operate about a fixed pivot 811. on the base i3.

For illustrative purposes it is pointed out that in one concrete embodiment of the invention the stationary insulators it were located on thirtyeight inch centers with the rotatable insulator #5 located midway therebetween. The arm l9 had an effective length from the center 85 of rotation of the insulator 55 to the pivot point 83 of seven inches. The distance between the pivot points and 82 was live inches while the distance between the pivot points 82 and 8 was eight inches. The pivot point as was located on a circle whose radius was fourteen inches and whose center coincided with the center of rotation of the insulator i5. Further the pivot point 84 was oifset from a line, represented by the broken line tiifi through the centers of the insulators l4 and i5 by one and five-eighths inches. It will be understood that the 1ine85 is in the plane which is normal to the base 13 and includes the longitudinal axis or "the switch blade 26 when it is in the switch closed position. pivot point 8t is "located on the side of the line 86 toward the direction in which the switch blade It's-wings toward the open circuit position. The purpose of offsetting the pivot point "St in this manner is to reduce to a minimum the sidewise movement of the interphase rods ll as they move generally longitudinally to and from the switch closed position.

It is desirable to lock each of the switch blades 2'6 in'the switch closed position. One reason for this is to avoid accidental opening of the switch units It in the event that exceedingly heavy current flow takes place therethrough and magnetic reactions areoleveloped which tend to swing the switch blades 25 to the open position. For this purpose the toggle operating mechanism it iscOnStructed so that the links '3! and 83 thereof "canswing slightly past a position where they are in 'end to-end centered relation. A stop ill is carried by each of the bases it and is located in the path of the relatively long toggle link 83 so a's'to limit the movement thereof past the center position. At the same time, because the toggle links 31 and '83, as shown in Fi ure 4-, are in the over center position and react against the stop 8'7, any force tending to rotate the insulator it or the switch blade'25 carried thereby is prevented from effecting such rotation because of the over center locked position of the toggle links 81 and 83.

"Since the toggle operating mechanism it swings p'ast'the centered position when. the switch is closed, the adjustment of the various pivot points is made non critical and. the mechanism 'c'a'nb'e factory assembled for simplified field erection. Also this arrangement permits all of the 5o'ints of the operating mechanism to be broken loose before any movement of the switch blade takes place. This feature is particularly advantageous under conditions of corrosion, sleet and 109.

'While the arrangement of the arms '59 and the toggle links 8'! and -83 is such that the switch blade '26 of each switch unit is is operated only to the full open position which is ninety de rees away 'irorn the switch-closed position, it des'i-rable to reduce the shock incident to the sw inging'of each of the switch blades it to the open position. For this purpose a resili nt bumper 5 i preferably formed of rubber, is mounte'd'on a bracket 92 that carried by the base i 3. The bumper Si is located in the path of move ment of the arm 89 and is arranged to be en- 'gaged thereby when it approaches the position corresponding to the full open position of the "switch blade. The bumper or also prevents the arm l9 and link 25 from rnoving into tOEeNQ locking positions.

The-operation of each of the switch units i2 is accomplished by rocking the relatively long toggle link 83 away from the stop 81' in a counterclockwise direction. This is accomplished preferably by connecting the operating mechanism to the pivotal connection between the toggle links 8! and '83. The only force then acting on the pivot 84 is that which'is transmitted thereto along the link 33. As shown in Figure 4 this is accomplished through the provision of coupling members 93 and 9 2 It will'be understood that they are arranged to be connected to the rods 'i-l 6 and r8, previously referred to, for simultaneous gang operation of the switch units l2.

In describing the functioning or the toggle operating rh'echani'sm it, reference may be had to the diagrammaticillustrationin Figure 5. The pivot point 82, when it is located at A, correspon'ds to the position shown in Figure 4.- where the 'toggle -links 8! and 83 are in the over center toggle locked position against the stop 8l. When the toggle link 83 is swung through an angle of a few deg-reea the pivot 'pointBZ is swung to the position B where the toggle links '8! and 83 are in end-to-end centered relationship. During this movement from n to B substantially no movement of the pivot point so takes place be" cause of lost motion in the pivotal connections. There is then no change in the position of the main contact arm 29 with respect to the stationary main contact member 36.

As the toggle link 83 is rocked in the counter clockwise direction soas to shift the pivot point 32 from the position LB, this pivot point follows along the arc 95. This is accompanied by movement of the pivot point Bil at the outer end-of the arm '59 along the are 95. When the pivot point 8c is swungto the position C and the pivot point'iZ occupies the position D, the switch blade 25 has been swung through ninety degrees from the switch closedto the switch open position. A reversal. of this movement caused by a rocking of the toggle link .83 in a clockwise direction causes the pivot point Bil to swing along the arc back to its initial position corresponding to the switch closed position.

The relationship between the movement of the toggle link '83 and the corresponding movement of the switch blade '25 is ilustrated by the curve 92' in Figure *6 "of the drawings. It will be observed that this curve is plotted with movement of the toggle link we as abscissas and movement of the switch blade 26 away from the closed position as ordinates. 'Thecurve is drawn for comparison to illustrate what the straight line relationship would be if the movement of the switch "blade 2e corresponded exactly to the movement of the togglelink 8t.

Particularly with-reference to the curve 9'? and to the initial portion 99 thereof, it will be noted that during the initialopening movement of the toggle link 83 through a considerable extent there is 'only'a slight movement of the switch blade 26 to effect the separation of the main contact arm from thestationary main contact 36 at each end. This mechanical advantage relationship then provides the necessary .force required to overcome the biasing action of the contact lingers on the maincontact arms and to overcome conditions'of corrosion, sleet and ice without requir i-ng that undue :force be applied to the toggle link 83 by the operating mechanism, such as the manually operable handle 22.

As illustrated at the portion or". curve ill the movement of the switch blade it is accelerated with respect to the movement of operatmechanism for the load interrupter :32 for moving the movable contact thereof toward the open position at a relatively high speed for in terrupting the circuit and drawing an are within the load interrupter 42.

The curve ill shows that, after the switch blade '25 has effected the operation of the load interrupter 42, its movement approximates that orthetogglelink'ilt during the remainder of the movement ofthe's'wi'tch blade 2'8 to the switch open position.

When the switch blade 26 is swung to "the switch closed position this sequence of movement is reversed. That is, when the switch blade 26 swings past the load interrupter 42 at each end, it eiiects the operation of its contacts to close the circuit at an accelerated speed as compared to the speed of swinging movement of the link 83. Then, when the main contact arm 39 en gages the contact fingers and a relatively great force is required for completing the closing action of the switch, the toggle link 33 swings through a relatively large arc while the switch blade 25 is completing its travel and swinging through a relatively small arc with a corresponding multiplication in the force applied by the toggle link 83 received from the operating mechanism at the pivot point 82.

Since certain changes can be made in the foregoing construction and different embodiments of the invention can be made without departing from the spirit and scope thereof, it is intended that all matter shown in the accompanying drawings and described hereinbefore shall be in terpreted as illustrative and not in a limiting sense.

What is claimed as new is:

l. Mechanism for operating a switch blade carried by and movable with an insulator rotatably mounted on a base carrying in spaced relation a stationary insulator on which are mounted main contacts r quiring relatively great force for disengagement and engagement by said witch blade and a load interrupter requiring relatively high speed operation by movement of said switch blade following such disengagement and prior to such engagement comprising, in combination, an arm rigidly attached to said rotatable insulator, a relatively short toggle link pivoted at one end to said a relatively long toggle link pivoted at one end to the other end of said relatively short toggle link and at the other end pivoted to said base at a point offset on the side toward opening movement of said switch blade from a plane perpendicular to said base and containing the longitudinal axis of said switch blade in switch closed position, said toggle links being in end-to-end centered position when said switch blade is in closed position and movable slightly past said centered position to lock said sw' ch blade in closed position, stop means for limiting the movement of said toggle links past center position, and driving means connected to the pivotal connection between said toggle links for moving them to swing said switch blade from and to its locked switch closed position to and from its switch open position.

2. Mechanism for operating a switch blade carried by and movable with an insulator rotatably mounted on a base carrying in spaced relation a stationary insulator on which are mounted main contacts requiring relatively great force for disengagement and engagement by said switch blade and a load interrupter requiring relatively high speed operation by movement of said switch blade following such disengagement and prior to such engagement comprising, in combination, an arm rigidly attached to said rotatable insulator, a relatively short toggle link pivoted at one end to said arm, a relatively long toggle link pivoted at one end to the other end of said relatively short toggle link and at the other end pivoted to said base at a point oiiset on the side toward opening movement of said switch blade from a plane perpendicular to said base and containing the longitudinal axis of said switch blade in switch closed position, said toggle links being in 8 end-to-end centered position when said switch blade is in closed position, and driving means connected to the pivotal connection between said toggle links for moving them to swing said switch blade from and to its switch closed position to and from its switch open position.

3. Mechanism for operating a switch blade carried by and movable with an insulator rotatably mounted on a base carrying in spaced relation a stationary insulator on which are mounted main contacts requiring relatively great force for disengagement and engagement by said switch blade and a load interrupter requiring relatively high speed operation by movement of said switch blade following such disengagement and prior to such engagement comprising, in combination, an arm rigidly attached to said rotatable insulator, a relatively short toggle link pivoted at one end to said arm, a relatively long toggle link pivoted at one end to the other end of said relatively short toggle link and at the other end pivoted to said base at a point offset on the side toward opening movement of said switch blade from a plane perpendicular to said base and containing the longitudinal axis of said switch blade in switch closed position, said toggle links being in end-to-end centered position when said switch blade is in closed position, and driving means connected to the pivotal connection between said toggle links to move the pivotal connection therebetween through a relatively great distance while said switch blade is being swung through a relatively short distance from and to its switch closed position and to accelerate the movement of said switch blade over the movement of said pivotal connection while said witch blade is operating said load interrupter.

4. Mechanism for operating a switch blade carried by and movable with an insulator rotatably mounted on a base carrying in spaced relation a stationary insulator on which are mounted main contacts requiring relatively great force for disengagement and engagement by said switch blade and a load interrupter requiring relatively high speed operation by movement of said switch blade following such disengagement and prior to such engagement comprising, in combination, an arm rigidly attached to said rotatable insulator, a relatively short toggle link pivoted at one end to said arm, a relatively long toggle link pivoted at one end to the other end of said relatively short toggle link and at the other end pivoted to said base at a. point offset on the side toward opening movement of said switch blade from a plane perpendicular to base and containing the longitudinal axis of said switch blade in switch closed position, said toggle links being in end-toend centered position when said switch blade is in closed position and movable slightly past said centered position to lock said sv' tch blade in closed position, stop means for limiting the movement of said toggle links past their center position, and driving means connected to the pivotal connection between said toggle links to move the pivotal connection therebetween through a relatively great distance while said switch blade is being swung through a relatively short distance from and to its switch closed position and to accelerate the movement or" said switch blade over the movement of said pivotal connection while said switch blade is operating said lead interrupter.

5. Mechanism for operating a switch blade carried by and movable with an insulator rotatably mounted on a base carrying in spaced relation a stationary insulator on which are-mounted main contactsv requiring relatively reat, force for? disengagement and en agement by said switch blade and a load interrupter requiring relatively high operation by movement of said switch blade following such disengagement and prior to such engagement comprising, in combination, an arm rigidly attached. to said rotatable insulator; arelatively short tog le link pivoted at one end to said arm, a relatively long toggle link pivoted at one end to the other of sai relatively short toggle link andatthe other end pivoted to said base at a point offset on the side toward opening movement of said switch blade from a plane perpendicular to said base and containing the longitudinal axis of said switch blade in switch closed position, said toggle links being in end-to-end centered position when said switch blade is in closed position and movable slightly past said centered position to lock said switch blade in closed position, a stop carried by said base and cooperating with said relatively long toggle link to limit the movement of said toggle links past their center position, and driving means connected to the pivotal connection between said toggle link for moving them to swing said switch blade from and to its locked switch closed position to and from its switch open position.

6. Mechanism for opera ting a switch blade carried by and movable with an insulator rotatably mounted on a base midway between two stationary insulators carried thereby on each of which are mounted main contacts requiring relatively great force for disengagement and engagement by said switch blade and a load interrupter requiring relatively high speed operation by movement of said switch blade following such disengagement and prior to such engagement comprising, in combination, an arm rigidly attached to said rotatable insulator, a relatively short toggle link pivoted at one end to said arm, a relatively long toggle link iVO'ted at one end to the other end of said relatively short toggle link and at the other end pivoted to said base at a point offset on the side toward opening movement of said switch blade from a plane perpendicular to said base and containing the longitudinal axis of said switch blade in switch closed position, said toggle links being in end-to-end centered position when said switch blade is in closed position and movable slightly past said centered position to lock said switch blade in closed position, stop means carried by said base and cooperating with said toggle links to limit the movement thereof past their center position, and driving means connected to the pivotal connection between said toggle links for moving them to swing said switch blade from and to its locked switch closed position to and from its switch open position.

7. Mechanism for operating a switch blade carried by and movable with an insulator rotatably mounted on a base midway between two stationary insulators carried thereby on each of which are mounted main contacts requiring relatively great force for disengagement and engag ment by said switch blade and a load interrupter requiring relatively high speed operation by movement of said switch blade following such disengagement and prior to such engagement comprising, in combination, an arm rigidly attached to said rotatable insulator, a relatively short toggle link pivoted at one end to said arm, a relatively long toggle link pivoted at one end to the other end of said relatively short toggle link and at theother end-pivoted to said; base at a point offset on the, side toward opening movement of said switch blade from a plane perpenrdicular to said; base and containing tb longitue dinal axis. of said: switch blade itch closed position, said toggle links being in end-to-end centered position. whensaid; switch blade is in; closed position, and; driving means connected to the pivotal, connection, betweensaid tog le links, to move the pivotal. connection therebetweenthrough rel tively great; distance while. said: switch blade is being swung through a, relatively short distance from and to its switch closed position and to accelerate the movement of said switch blade over the movement of said pivotal connection while said switch blade is operating said load interrupters.

8. Mechanism for operating simultaneously a plurality of spaced apart switch blades each carried by and movable with an insulator rotatably mounted on a base carrying in spaced relation a stationary insulator on which are mounted main contacts requiring relatively great force for disengagement and engagement by the respective switch blade and a load interrupter requiring relatively high speed operation by movement or the respective switch blade following such disengagement and prior to such engagement comprising, in combination, an arm rigidly attached to each rotatable insulator, a relatively short toggle link pivoted at one end to each of said arms, a relatively long toggle link pivoted at one end to the other end of each of said relatively short toggle links and at the other end to the respective base at a point offset on the side toward opening movement of the respective switch blade from a plane perpendicular to the respective base and containing the longitudinal axis of the respective switch blade in switch closed position, the toggle links of each set being in end-toend centered position when the respective switch blade is in closed position and movable slightly past said centered position to lock the respective switch blade in closed position, stop means carried by each base and cooperating with the respective set of toggle links to limit the movement thereof past their center position, and driving means commonly connected to the pivotal connection between the toggle links of each set for moving them to swing the respective switch blades from and to their locked switch closed positions to and from their switch open positions.

9. Mechanism for operating simultaneously a plurality of spaced apart switch blades each carried by and movable with an insulator rotatably mounted on a base carrying in spaced relation a stationary insulator on which are mounted main contacts requiring relatively great force for disengagement and engagement by the respective switch blade and a load interrupter requiring relatively high speed operation by movement of the respective switch blade following such disengagement and prior to such engagement comprising, in combination, an arm rigidly attached to each rotatable insulator, a relatively short toggle link pivoted at one end to each of said arms, a relatively long toggle link pivoted at one end to the other end of each of said relatively short toggle links and at the other end to the respective base at a point offset on the side toward opening movement of the respective switch blade from a plane perpendicular to the respective base and containing the longitudinal axis of the respective switch blade in a toggle link connection individual thereto while the former is operating the respective load interrupter.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,815,392 Alsaker July 21, 1931 2,194,021 Johnson Mar. 19, 1940 2,470,576 Pollock et al May 1'7, 1949 2,579,798 Crabbs Dec. 25, 1951 

